Paeds Elective iSAWE 8

Question

A 3 year old girl refuses to walk, with a temperature of 39 degrees, a WCC of 15 and an ESR of 55. Ultrasound shows a left hip effusion.

Paeds Elective iSAWE 8, ultrasound of the hip
Ultrasound of the hip. Image by Article authors, Ruiz Santiago, Fernando, Santiago Chinchilla, Alicia, Wikimedia Commons, CC BY 4.0.
  1. How do you distinguish septic arthritis from transient synovitis?
  2. What is your management?
  3. What are the complications?

Answer

Septic arthritis versus transient synovitis

  • Kocher criteria are inability to weight bear, fever over 38.5 degrees, ESR over 40 mm/hr and white cell count over 12 x 109/L
  • Probability of septic arthritis is about 3% with one criterion, 40% with two, 93% with three and over 99% with all four
  • CRP over 20 mg/L adds predictive value
  • This child meets all four criteria

Management

  • Blood cultures, then ultrasound guided aspiration for Gram stain, culture and PCR, as Kingella kingae is common under 4 years
  • Urgent arthrotomy or arthroscopic washout of the hip
  • Empirical intravenous antibiotics such as flucloxacillin or cefazolin, adjusted to cultures
  • Early switch to oral antibiotics when clinically improving and CRP falls, for a total of about 3 weeks
  • MRI if not improving, to look for adjacent osteomyelitis or abscess

Complications

  • Avascular necrosis of the femoral head
  • Physeal damage with leg length discrepancy and deformity
  • Chondrolysis, dislocation and joint destruction with delay
  • Recurrent infection and chronic osteomyelitis

Related pages

Author Contributions

Orthofracs team

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.